Muffle furnace



J. K. CARSKADDON.

MUFFLE FURNACE. APPLICATION FILED JUNE I8; 192].

1 432 667, Patgnted Oct. 17, 1922.

wiftaadazz Patented aarvr'nsxnureaesx annon, or IEARSON, WASHING-TON.

inn-r'FLE FURNACE.

'a ncanen fired June 18,1921. Serial No. 478,481.

To all whom it may concern:

Be itknown that I, JAMES K. CARSKADDON, a citizen ofthe United States "of America, and resident of the "town of Pearson,in the county of Kitsap and State'of Washington, jhave' 'invented certain-new and useful Improvements in Muflle Furnaces, of which the *following is a specification. My. invention relates to muilie furnaces jand particularly to a mulfle furnace of a small size, -such "as is "suited I130 'baking'of "teeth, which is a frequent job in dental @olii'ces. Y f a The-object of "my invention is to provide an efiective' small'furnace suited to this type of use which will be cheap in construction arid which will be durable and have long 1i e.

5 The features of my invention upon which I desire to obtain 'a patentwill be 'h'erein- ,aaer described and then particularly defined bythe claims. I

The accompanying-"drawings show my invention "embodied in the type of construction which I now most prefer to use. 7 Figure lisa longitudinalsection through theax'i's of'the furnace.

Figure 2 is an end elevation of the furnace, taken from the side opposite thatat which the"'gas-is"appliedthereto.

Figure 3 is a section takenupon the line 3"'-3-of Figure This furna'ce lras an outer shell,'{an inner muffle caseyarid 'a'mufliewhic'h is designed for removable insertion in the muifle casing. The main body of the outer shell consists of a tubular shell 1 which is composed of some suitable refractory material such for instance, as fire clay. To prevent crack- 40 same with a slit, as 10, extending lengthwise thereof. This permits free expansion and contraction without producing undue strains within the body of the shell.

The ends of the main shell 1 are closed by two end plates 2 and 3. These are each provided with openings somewhere adjacent to or just above the center thereof for the reception of the Inufile, for the entrance of the heating gas and for the escape of the hot gases. These end plates, which close the shell 1, are also provided each with a slot, as 20, extending from the opening for the mufile to the outer edge thereof. The purpose of this is also to relieve the plate from side of the muflie.

ing of this under heat, I have provided the theinternal strains caused by heating and VVithin the chamber formed by the tubular shown at 10 in Figure 1. This is placed "toward the end of the furnace at which the heated "gas is -introduced.

The upper side of this mullle casing may be slit, as shown at-" 12, to permit expansion and contraction, as lnth'e case of th'eouter shell 1.

'At 13 is shown a conventional representati'on'of a gas burner. This is placed so "as'to dischargeits j'et into the'opening '30 in the plate 3, this being positioned also so "as-to dischargethe flame upon the downwardly curved floor section 4L0 of the muffle casing and thus under the muiile. This will result in lreatlng the floor of the muffle casing and in deflecting the heat upwardly towardthe mullie 5. The opening 30 in the end plate 8 may be of any suitable shape "and ofatsiz'ewhich will permit, satisfactory entrance to theflame and the air which is associated therewith. The hole in the opposite end plate 2 is made of an irregular shape,wl1ichis best shown in Figure 2. .This consists "of an opening of a size to 3 modified by external projections or lobes, as 21, which form gas escape passages out- One'e'nd of the muffle, the same being the open end, is made of a shape and size to fit within this opening in the plate 2 and be supported thereby. The muflie is also provided with a lug, as 50, projecting from its bottom and engaging with the floor of the muflie casing 1, so as to assist in the support of the mufile. By reason of the engagement of the open end of the muffle with the walls of the open ing in the plate 2 and the support of the inner part thereof by the lug 50, the muffle is supported with its walls spaced away from the casing 4 and the gases, therefore, have free opportunity to circulate about the same.

The end of the muffle casing 4 which is towards the discharge end of the furnace, is cut backard on an incline, as is shown at 41. This forms a communication between the chamber within the mufiie casing and its surrounding chamber. The end plate 2 also cooling and prevent its cracking elsewhere.

has a ledge 22 projecting inwardly in such position as to form a support for that end of the mufiie casing. The other end of the muffle casing may be extended so as to be supported from the lower portion of the tubular shell 1. v

I prefer to enclose the outer shell 1 with a layer, as 6, of asbestos or other heat insulating material and the whole is bound together by a sheet, 7, of sheet metal, the" endsof which are crimped over sufficiently to hold the end plates 2 and 3 in position andthe ends of said plate 7 being of sufficient length to be joined together and secured as by bolts 70 and to then be flared outward, as

shown at 71, to form a base or legs for supporting the same.

The above construction of furnace is one which is easil made and quite simple. The slotting of t e tubular casing l and the muflie shell 4 lengthwise relieves them from internal strain to such an extent that they are not likely to crack. It istherefore possible to use them many times in succession. The muffle 5 is intendedto be removed as desired. The opening in the end disk 2 throughwhich the muffle is inserted is provided with a downwardly extending lobe 21, so positioned as to pass the lug 50.

What I claim as my invention is 2v 1. A muiiie furnace having a muffle casing which is slit lengthwise along one side.

2. A mufiie furnace having a muffle casing having its lower side inclined downward at the flame receiving end and. slit lengthwise along its top. a y y 3. A muflie furnace having a muffle casing having its floor inclined downward at the flame receiving end, its opposite end inclined backward towards its top, and its upper side slit lengthwise.

4c. A muffle furnace having a refractory outer tube which is slit lengthwise, end

plates forming closures for said tube and provided withmuflle receiving openings and a one side slit from said opening to its pe riphery, a mufiie casing fitting within said tube and having one end enlarged by a downward inclination of its floor, and a muffle having an end having supporting engagement with one end plate and a supporting lug extending between-muffle and muffle casing.

5. muffle furnace having acylindrical shell, end closing plates having muffle openings and slit at one side from said opening to its outer edge, a muffle casing havingits floor at oneend inclined downward and lengthwise slit" along its upper side, the end plate at the other end having a ledge for supporting the muffle casing, a muffle having its open end fitting in and supported from the walls of the opening in the end plate and a lug engaging the floor of the mufie casing, said opening in the end plate having outward extensions for discharge of gas.

6. A muffle furnace having an outer shell which is slit lengthwise along one side.

7. mufiie furnace havingan outer shell slit lengthwise along one side, and a muffle casing supported therein and likewise slit lengthwise along one side.

8 A muffle furnace having an. outer shell slit lengthwise alon one side, and a muflie casing supported t erein and having its lower side inclined downward atthe flame receiving end.

9. A muflle furnace having an outer shell whichis slit lengthwisealong one side, and end plates forming closures for saidshell and provided with muffle receiving openings, and at one side slitfrom said opening to its periphery.

Signed at Seattle, King County, Washington, this 10th day of June, 1921. Y

J AMES- KENT CARSKADDON. 

